SIMON A.T. REDFERN, C. MICHAEL B. HENDERSON
The high-temperature cell parameters of K2MgSis012 have been measured by X-ray powder diffraction between room temperature and 842 K. A first-order ferroelastic phase transition between the room-temperature P2/c structure and a high-temperature Pbca structure occurs at 622 K. The spontaneous strain behaves as the order parameter for the transition, following a simple Landau model. Simple lattice dynamics simulation of the magnesiosilicate framework reveals that acoustic mode softening drives the elastic instability. The first-order character of the transition is attributed to a large excess volume, which arises from collapse of the framework around the alkali site. At higher temperatures, the orthorhombic cell edges converge toward a metrically cubic structure, but this transformation requires Mg-Si disorder, which was not observed on the time scale of these experiments.
@article{ae3878f2-ce48-437f-9ad0-42a242392d8d,
title={Monoclinic-orthorhombic phase transition in the K2MgSis012 leucite analog},
author={SIMON A.T. REDFERN and C. MICHAEL B. HENDERSON},
year={1996},
language={en}
}TY - JOUR TI - Monoclinic-orthorhombic phase transition in the K2MgSis012 leucite analog AU - SIMON A.T. REDFERN AU - C. MICHAEL B. HENDERSON PY - 1996 LA - en ER -
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